unfortunately most of those stats are meaningless unless you compare two cards with a similar core chip. otherwise there are countless instances where cards with faster RAM, core speed, bandwidth, shaders, etc., lose out to cards that on paper have less to offer the consumer.
the key to making any video card purchase is head to head benchmarks.
tom's hierarchy chart
http://www.tomshardware.com/reviews/radeon-hd-6950-1gb-...
and anandtech's benchmark tool
http://www.anandtech.com/bench/GPU/88
are two good places to start